The chemical potential of the immune system was underscored when it was shown in 1986 that antibodies raised to tetrahedral, negatively-charged phosphate and phosphonate transition state analogues were capable of selectively catalyzing the hydrolysis of carbonates and esters, respectively. Since that time antibodies have been generated that selectively catalyze a wide array of chemical reactions. Because antibodies can be generated that bind almost any molecule of interest, this new technology offers the potential to tailormake highly selective catalysts for applications in biology, chemistry and medicine. In addition, catalytic antibodies provide fundamental insight into important aspects of biological catalysis, including the importance of transition-state stabilization, proximity effects, general acid and base catalysts, electrophilic and nucleophilic catalysis, and strain. Our specific aims in this proposal are (1) to characterize the catalytic mechanisms and structures of three previously generated catalytic antibodies - a chorismate mutase, nucleoside acylase and cis-- trans enone isomerase. This work will provide important mechanistic information into the nature of antibody catalysis that will be relevant to the generation of more efficient catalytic antibodies, (2) to use selection schemes coupled with random mutagenesis to increase the catalytic efficiencies of existing antibodies. This may prove a powerful general strategy for optimizing antibody catalysts, (3) to develop general strategies for generating antibodies that selectively cleave amide bonds. This work might lead to sequence specific peptidases for applications in biology and medicine and (4) to generate and characterize antibodies that catalyze rotation around a sigma bond, a mechanistically simple unimolecular reaction in which transition state stabilization can be easily quantitated.